The CZ method is one of methods for manufacturing a single crystal silicon.
A single crystal silicon (ingot) which has been grown and pulled by the CZ method is sliced, polished and etched to be provided as a silicon wafer for the fabrication of a semiconductor device.
Specifically, the single crystal silicon is pulled from a melt that has been doped with an impurity such as boron B so as to give the silicon wafer a desired resistivity.
In the course of pulling the single crystal silicon, the impurity is not introduced uniformly into the single crystal silicon. Therefore, if a silicon wafer produced from the single crystal silicon (ingot) that has been grown in this manner is cut vertically (perpendicularly to the wafer surface), growth striations corresponding to the impurity concentration nonuniformity are observed and, in the wafer surface, ring-shaped impurity concentration nonuniformity is observed.
Whereas, in recent years, some types of semiconductor devices require demanding specifications for surface planarity of silicon wafers.
As a prior art technique relative to the present invention, the below-mentioned patent document 1 is known.
In this patent document 1, attention is paid to oxygen that is introduced into a single crystal silicon from a quartz crucible via a melt, and the invention disclosed therein is intended to reduce the nonuniformity in oxygen concentration appearing in the surface of a silicon wafer. According to this prior art, the oxygen concentration nonuniformity appearing in the surface of a silicon wafer is reduced by setting the ratio h/d of an overlap length h of a heater slit to an inner diameter of the heater to 0.70 or lower.
Patent document 1: Japanese Patent Application Laid-Open No. 11-116390